Keeping communications secret from an adversary or competitor has long been the challenge of the military, agencies of the federal government as well companies that are targets of corporate espionage. The challenge becomes even more difficult when communications are made from locations that do not have structures that have been built to prevent eavesdropping and the like, such as when a member of the presidential cabinet, foreign service or military travels to a foreign country, works in an embassy built by some other country or travels to a locale within the United States that is not considered secure from a communications point of view.
One method of ensuring that communications remain secure in the situations described above, and others, is to put communications equipment inside a portable, shielded enclosure. One example is a tent made from a special fabric that prevents eavesdropping and leakage of communication signals (e.g., radio frequency, “RF”, signals). Whenever communications need to be secure, an individual walks into the enclosure, closes the enclosure and uses the communications equipment installed within the enclosure to send and receive communications.
Though such enclosures make it more difficult to conduct eavesdropping and reduce potential leakage of signals, they are not fool proof. For example, though the equipment inside the enclosure may be secure such equipment must receive sufficient power from the outside. Further, if communications are conducted over wired links such wires must be connected through the walls or “skin” (i.e., surfaces) of the enclosure.
Existing enclosures include an access panel or opening through which power and signal wires may pass. Because eavesdropping and leakage is possible through such an opening and over such wires a specially designed filter assembly is used. The assembly is designed to be attached to, and fit into, the opening. Once installed in the opening the signal and power wires from the outside are connected to the exterior side of the assembly while interior wires leading to communications equipment and the like are connected to the interior side of the assembly. Existing assemblies include a specially designed and machined metal frame. Attached to the frame are specially designed electronic and electrical filters. Once attached to the frame, the filters are then placed between the exterior and interior wires to ensure that unwanted communication or power signals are not allowed to pass into the enclosure and unsecure communication signals are not allowed to escape.
Existing assemblies require the use of many fasteners, such as screws and bolts to fasten the filters to the metal frame. FIG. 1 depicts an example of an existing assembly 1. As shown, sixteen screws 2 must be used to install a flange 3 to the frame 4. The flange 3 is needed to make sure a power filter 5 is physically connected to the assembly 1. The danger is that communication signals may leak out from within the enclosure through the small openings formed by each screw 2. Given the sophistication of today's eavesdropping techniques, even small leaks can provide an adversary with enough information to place people's lives at risk.
Accordingly, what is needed are improved methods and devices for reducing communication and power signal leakages from filter assemblies, shielded enclosures and the like.